Analog, scen optimization in Bryce is tediuos, but not impossible. What kinds of lights are you using? Lights with "ranged" falloff render the fastest. And of course, lights that don't cast shadows render even faster. Are you using Volumetric World? Don't, it's obnoxious and slow and there are plenty of volumetric workarounds you can use that will not only look BETTER, but will give you some control over their render speeds... Get back to us, start a new thread and we'll help you take that scene apart...